This invention relates to a mechanical connector for connecting tubular members. More specifically, this invention relates to a connector having a latch guide mechanism and a safety piston for urging the latch to an unlatched position.
Remotely operated mechanical connectors are used in the oil and gas recovery industry to join generally tubular members. Such connectors typically have the following features:
1. A pair of tubular members to be joined together. Each member bears one or more load shoulders or teeth. Typically, such teeth on a tubular member appear as a series of alternating grooves and ridges.
2. A latch consisting of one or more load shoulders or teeth. The latch is typically disposed about the perimeter of the tubular members in the form of one or more ring segments. The teeth on the latch mate with grooves about the ends of the tubular member to mesh and hold the parts together. Radial movement of the latch ring allows the teeth to be engaged or disengaged.
3. The teeth on the tubular members and latch ring each have a load flank and a stab or back flank. The load flanks of the teeth of the tubular members firmly contact the corresponding load flanks on the mating teeth on the latch ring.
4. Typically, the load flanks of the teeth form a series of conic surfaces around the tubular members and on the inside of the latching ring. The flanks may be angled in such a way that squeezing the latching ring (either whole or segmented) around both of the members results in their being drawn together. This axial movement and force is desirable for a number of reasons, such as to:
Mate or face up the tubular members against an outside resistance or imposed misalignment;
Compress, energize, or otherwise set a gasket or sealing element between or within one or both of the tubular members;
Elastically load, stretch, deflect or otherwise energize the mechanical elements of the connection. This is typically beneficial for keeping a seal and minimizing the fluctuation of stress when the connector is subjected to a variety of fluctuating load conditions.
Compensate for uncertainties of fit and manufacture between the tubular members and other connection components.
5. A primary mechanism, i.e., cams or other moving, impinging surfaces, holds the latch in firm contact with the tubular members. It also applies force to translate the latch from the open position to the engaged position.
6. The primary mechanism applies the force needed to draw the tubular members together and preload them.
7. The latch ring may have a spring bias (inherent or externally applied) to push it either inward or outward, and either towards or away from the mating teeth on the tubular members.
8. The connector must be made to reliably disengage when the duration of service is ended.
Connectors of this type are used within the offshore oil industry to tie a producing wellhead to a riser and production platform. Connectors of this nature must withstand a variety of factors present in large, deepwater developments. Among these are high contained pressures (up to 10,000 psi), high loads (up to millions of pounds tension and foot-pounds bending), long life (20+years), fatigue effects, corrosive environments, and remote operation. Finally, when the well is exhausted, the connection must be removed to decommission the well and allow the production platform to be used elsewhere. Due to the value of the product, and the time-rate cost of all the other high-performance equipment used in association with these connectors, a high premium is placed upon reliability and ease of use.
Two of the aforementioned factors that influence the reliability and ease of use of these connectors are especially germane to the present invention. First, remote operation implies less ability to adjust, control, or finesse the operation of a piece of machinery without careful preparation and design. Second, the long exposure to the deep sea environment and load conditions may make it difficult for the connector to disengage from the wellhead. Causes may include permanent deformation of the latching elements, corrosion, galling/welding, or encrustation by product fluids (methane hydrate ice, wax, asphalts, etc.). An improved connector is therefore desired that is easier to maneuver and is more reliable, especially for use in a harsh, remote location.
The disadvantage of the prior art are overcome by the present invention, and an improved connector assembly and method are hereinafter disclosed.
A tubular connection is provided for connecting an upper tubular member with a lower tubular member. A radially movable latch body may be positioned outward of each tubular member. At least one inner load flank on each tubular member may be angled with respect to an axis substantially defined by the tubular members. A plurality of outer load flanks on the latch body slidably engage the at least one inner load flank of each tubular member to urge the tubular members axially together. A radially projecting member is fixed to one of the latch body and a one of the tubular members, and a guide recess is provided in the other of the latch body and the one of the tubular members. The guide recess receives the radially projecting member to guide the latch along a desired trajectory with respect to the tubular members when the latch body is moved radially between an unlatch and a latch positions.
A trajectory may be chosen to determine movement of the load flanks on the latch body relative to the respective load flanks on the tubular members. One or both of a length of the radially projecting member and a depth of the guide recess may be selected to limit motion of the latch with respect to the tubular members. The radially projecting member may be at least partially positioned within the guide recess when the latch body is in a radially outward or unlatched position.
The tubular connection may further comprise a safety actuator axially movable with respect to the latch body. A safety shoulder may be fixed with respect to the latch body and engageable by the safety actuator. The safety shoulder may be angled inwardly to urge the latch radially outwardly to the unlatched position. The safety actuator may be hydraulically or pneumatically activated.
A cam member may be included for urging the latch radially inwardly. The cam member may include a cam surface engageable with and angled with respect to the latch body, and is movable axially with respect to the tubular members. The cam member may also be hydraulically or pneumatically activated.
At least one sealing member may be disposed between the upper and lower tubular members for sealing between the tubular members. A load shoulder preferably is also included on each of the upper and lower tubular members. The load shoulders contact to support an axial load between the upper and lower tubular members.
A bias member may be provided for biasing the latch body radially inwardly or outwardly. The bias member may be a spring disposed within or about the latch body, or the latch body may comprise a c-ring or a set of dog/collet segments.
It is an object of this invention to provide a method for connecting an upper tubular member with a lower tubular member. The method includes providing a radially moveable latch body outward of the tubular members, forming at least one inner load flank on each tubular member, with each load flank angled with respect to and radially disposed about an axis of the tubular members, and a plurality of outer load flanks on to the latch body engageable with the at least one inner load flank of each tubular member. The method may include determining a desired trajectory of the inner load flanks with respect to the outer load flanks, and providing a radially projecting member on one of the latch body and one of the tubular members, and a guide recess in the other of the latch body and the tubular members for receiving the radially projecting member and guiding it along the desired trajectory. The latch body may be urged radially inwardly to engage the at least one inner load flank with at least one outer load flank to urge the tubular members axially together.
The method may further comprise providing a cam member having a cam surface angled with respect to the latch body. The cam member may be moved axially with respect to the latch body to urge the latch body radially inwardly. A safety actuator may be provided axially movable with respect to the latch body, and a safety shoulder may be fixed with respect to the latch body. The safety shoulder may be angled inwardly to urge the latch radially outwardly.
These and further objects, features, and advantages of the present invention will become apparent from the following detailed description, wherein reference is made to the figures in the accompanying drawings.